1. Field of the Invention
The invention relates to an optical device and a light source controlling method thereof, in particular, to a projector and a light source controlling method thereof.
2. Description of Related Art
A projection device can project an image onto a large screen for the convenience of viewing by lots of people at the same time, so the projection device is commonly applied in public places like companies or schools. Moreover, in the development trend of the large scale of the home display products, the projection device is gradually popularized in common families and becomes an electronic product that is commonly seen in modern lives.
Along with the progress of technology, the portable micro projector (pico projector, or referred to as mini projector) has gradually become the mainstream for the future personal digital market. Generally speaking, a light source of the micro projector adopts a light emitting diode (LED) or another solid-state light source. When the micro projector is connected to the electronic device, the voltage provided by the electronic device serves as the operating voltage of the micro projector.
However, since the micro projector has to use the voltage of the electronic device, the stability of the internal voltage of the electronic device is influenced when the micro projector is connected to the electronic device. When the power of the voltage provided by the electronic device is relatively low, the abnormal running or even the auto shutdown of the electronic device may be caused when the micro projector is connected to the electronic device. In the situation of the abnormal running and the auto shutdown, the components of the electronic device are exposed to the risk of damages.
Taiwan Grant Patent No. 1307808 has disclosed a projection device, in which a connector of a power source circuit system is electrically connected to a USB connector of a computer by a USB cable, so that the computer provides a power source for the projection device. A casing of the projection device encapsulates a projection module, a driving module and the power source circuit system of the projection device and exposes some connectors of the power source circuit system.
Taiwan Grant Utility Model Patent No. M357153 has disclosed a projection device, which receives a power source and signal sent by a computer through a USB interface and a USB cable. The USB interface of the projection device may be connected to at least one USB interface of the computer, so as to receive the power source through the connected USB interface and receive the signal through one of the connected USB interface. The voltage of the power source received by the projection device is changed by a voltage control module and then transferred to a switching module. The switching module transfers the changed voltage to an image display module. The driving module of the projection device adjusts the current received by the USB interface from the computer and transfers the adjusted current to the image display module to change the display brightness of the image display module.